Thermoluminescence study of Cu,Ag and Mn doped lithium tetraborate single crystals and glasses

Spectrally resolved thermoluminescence (TL) of non-doped and Ag, Cu^? and Mn-doped lithium-tetraborate (LTB) single crystals revealed that TL emission bands for differently doped samples proved to be at different wavelengths: 272, 370 and 608 nm, respectively. These bands perfectly agree with the photoluminescence (PL) emission bands of Ag⁺, Cu⁺ and Mn²⁺ ions. It strongly points that these dopants are directly involved as recombination centers in the TL process.TL characteristics of non-doped and doped LTB single crystals and the corresponding glassy samples showed that their TL intensities and the structures of the glow curves were apparently different.     

Shape memory and phase transitions for auxetic materials

We present a mathematical model describing the auxetic‐austenitic phase transition phenomenon by a second order shape memory phase transition. The typical properties of auxetic materials, as the negative Poisson ratio ν, are described by a function of the phase ?, called order parameter, which relates the phase transition with a change of the internal order structure of the material. In our model, the auxetic phase is represented by an order parameter ? = 1, which provides a negative Poisson's ratio, while the austenitic phase will be denoted by ? = 0. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of phase transfer chemistry, segmented fluid flow, and sonication on the synthesis of cinnamic esters

Wittig reaction under Phase Transfer conditions was performed in a flow reaction system. Different bases, aldehydes, phosphonium salts, and flow reaction parameters were investigated, in absence of a phase transfert catalyst. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath.     

A new approach to glucose sensing at gold electrodes

An oxidative peak in the cathodic scan is observed in the cyclic voltammetry of glucose at gold electrodes, its peak current density being proportional to glucose concentration in a wide potential range. The application of this phenomenon in blood glucose sensing has been hindered by the presence of inhibitors: the most problematic are chlorides due to their high concentration and difficult separation from glucose. In the present paper we propose a solution to this problem involving a three electrode, four step pulsed electrochemical detection technique.     

Polyamide 6 treated with pentabromobenzyl acrylate and layered silicates

A study of the simultaneous application of a brominated flame retardant and an organically layered silicate (OLS) for the flame retarding of polyamide 6 (PA6) is presented. Upon treating PA6 with at least 7 wt% monomeric pentabromobenzyl acrylate (PMA), a UL‐94 V‐0 rating and an oxygen index (OI) value of 29.7 were obtained. By adding 1 wt% organically layered montorillonite (OMMT) and 10 wt% PMA, the V‐0 rating remained, indicating cooperation between PMA and OMMT. Higher concentrations of OMMT result in a decreased UL‐94 rating showing an antagonism. The size and mass of drops formed in the UL‐94 test increased with increasing OMMT, suggesting an increase in the viscosity and density of the pyrolyzing matrix. The effect of the Br additive on the peak heat release rate (PHRR) measured in the cone calorimeter is similar, but smaller, than that of clay. A calculation of the synergistic effectivity related to PHRR enabling a numerical estimate of the extent of synergism or antagonism is presented. When the ill‐dispersed pristine clay (Na⁺MMT) is used, the viscosity does not increase, the PHRR decreases slightly, but the mass loss rate (MLR) is close to that of the matrix. The time of ignition (TOI) decreases upon the addition of PMA, similarly to the addition of OMMT. This is explained by migration of the Br additive to the surface barrier similar to that of clay so that the low thermal conductivity (TC) barrier is formed before the ignition. Accumulation of heat in the barrier decreases the TOI. Copyright © 2010 John Wiley & Sons, Ltd.     

Expeditious synthesis of phenanthridines from benzylamines via dual palladium catalysis

A method for the synthesis of phenanthridines from benzylamines and aryl iodides which uses a dual palladium-catalyzed process is developed. The domino sequence ends via an intramolecular amination and an oxidative dehydrogenation. No protecting group or prefunctionalization of the amine is required, and the process uses dioxygen as the terminal oxidant.     

One-pot synthesis of a piperidine-based rigidified DTPA analogue and its bifunctional chelating agent

The core structure of cis-3,5-diaminopiperidine was N-alkylated with excess t-butylbromoacetate in order to exploit the successive N-quaternarization and Stevens rearrangement to access the pentaalkylated product and the bifunctional chelating agent containing a N-butanedioic acid pendant arm at the same time. The relaxometric properties of the Gd(III) complexes with these ligands were studied also in terms of pH and serum stabilities.     

Hybrid ligand-alkylating agents targeting telomeric G-quadruplex structures

The synthesis, physico-chemical properties and biological effects of a new class of naphthalene diimides (NDIs) capable of reversibly binding telomeric DNA and alkylate it through an electrophilic quinone methide moiety (QM), are reported. FRET and circular dichroism assays showed a marked stabilization and selectivity towards telomeric G4 DNA folded in a hybrid topology. NDI-QMs' alkylating properties revealed a good reactivity on single nucleosides and selectivity towards telomeric G4. A selected NDI was able to significantly impair the growth of melanoma cells by causing telomere dysfunction and down-regulation of telomerase expression. These findings points to our hybrid ligand-alkylating NDIs as possible tools for the development of novel targeted anticancer therapies.     

Water soluble extended naphthalene diimides as pH fluorescent sensors and G-quadruplex ligands

Extended naphthalene diimides (NDIs) fused to 1,4-dihydropyrazine-2,3-dione, containing two solubilizing moieties, have been synthesized. Fluorescence spectra of the new NDIs were remarkably affected by pH, as the second deprotonation of the dihydropyrazinedione moiety (pK(a) 6.9) switched off the emission. Binding to a G-quadruplex folded oligonucleotide and stoichiometry were evaluated by FRET melting assay and CD analysis. G-quadruplex binding was strongly enhanced shifting from pH 7.4 to pH 6.0 as a consequence of the dihydropyrazinedione moiety protonation. Cytotoxicity studies using two human telomerase-positive cell lines (HT29 and A549) revealed that the best G-quadruplex ligand was very active against the colon cell line, with an EC(50) of 300 nM.     

Tuning solid state luminescent properties in a hydrogen bonding-directed supramolecular assembly of bis-cyclometalated iridium(III) ethylenediamine complexes

Synthesis, crystal structural determination and photophysical properties of a series of heteroleptic cationic cyclometalated iridium(III) derivatives of general formula [(ppy)(2)Ir(en)]X (X = ClO(4)(-) (1), PF(6)(-) (2), Cl(-) (3), BPh(4)(-) (4)), are described. The assembly of the common molecular building block allows to get highly luminescent crystalline materials or to assemble poorly luminescent supramolecular channelled architectures, for which the additional contribution of oxygen quenching effects has been observed. Moreover, the high reproducibility of the preparations of the crystalline materials in their specific crystalline phases, makes the control of the supramolecular organization of photo-active iridium(III) complexes within the crystalline structures a useful synthetic procedure for the construction of highly luminescent materials.